President Obama arrived Sunday in Cuba, marking the start of an historic trip in which he’ll try to further improve U.S. relations with the isolated island country and encourage its communist leaders to make life better for their citizens.

The three-day trip follows Obama’s announcement roughly a year ago that his administration and the Cuban President Raul Castro's government would try to improve diplomatic relations after roughly a half-century of acrimony.

"I believe that the best way to advance American interests and values, and the best way to help the Cuban people improve their lives, is through engagement,” Obama said last month in announcing the trip. “I’ve always said that change won’t come to Cuba overnight. But as Cuba opens up, it will mean more opportunity and resources for ordinary Cubans. And we’re starting to see some progress.”

Americans have mixed views about the new alliance with the former Cold War foe.

Conservatives, including Cuban-Americans and others, see Obama's outreach as a disgraceful embrace of a government whose practices and human rights abuses betray American values.

"To this day, this is a regime that provides safe harbor to terrorists and to fugitives," said House Speaker Paul Ryan, R-Wis. "Unfortunately, it is doubtful that the president will bring up the need for reform during his visit."

However, others argue that the impoverished living conditions under which most Cubans live will never improve unless economic deals are forged and foreign investment -- including the construction of hotels and other tourism investments -- come into the country.

As part of their tour of Old Havana, the Obamas arrived at the Havana Cathedral in a heavy downpour, all carrying black umbrellas.

First lady Michelle Obama held her mother's hand as they walked gingerly on the slippery wet stones in the square in front of the cathedral.

A few hundred people who had gathered in the square erupted in applause and shouted President Barack Obama's name as the first family stepped forward.

The president spent a few minutes greeting some people in the crowd before the family entered the cathedral.

Republican presidential candidate Donald Trump took Cuban President Raul Castro to task for not welcoming Obama at the airport in Havana.

Trump tweeted: "Wow, President Obama just landed in Cuba, a big deal, and Raul Castro wasn't even there to greet him. He greeted Pope and others. No respect."

Trump has said if elected president he would try to negotiate a better deal with Cuba, but has also said he's "fine" with the U.S. pursuing a new approach. His top GOP rival, Ted Cruz, is the son of a Cuban and opposes Obama's policy.

Castro makes relatively few public appearances. But Castro did greet Pope Francis on arrival during a September trip to Cuba and Russian Orthodox Patriarch Kirill last month.

The White House however says it's taking no offense that Castro didn't greet Obama upon arrival.

Ben Rhodes, Obama's deputy national security adviser, says it was "never contemplated or discussed" that Castro would be at the airport.

He said the Cubans consider Monday morning's ceremony with Obama and Castro to be the official welcome event.

Several dignitaries were on hand at the airport, including Cuban Foreign Minister Bruno Rodriguez and Cuban Ambassador to the U.S. Jose Cabanas.

On Monday, Obama will meet with Castro in his presidential office before he will sit in the stands with baseball-crazed Cubans for a game between their beloved national team and Major League Baseball's Tampa Bay Rays.

Obama also will meet with political dissidents, whose experiences have shaped Cuban-Americans’ outrage over the president’s outreach.

White House officials are mindful that Obama cannot appear to gloss over deep and persistent differences. Even as the president works toward better ties, his statements alongside Castro and dissidents will be scrutinized for signs of how aggressively he is pushing the Havana government to fulfill promises of reform.

Cuban Foreign Minister Bruno Rodriguez rebuked Obama ahead of the trip for suggesting that he would use the visit to promote change. Rodriguez said that many of Obama's policy changes have essentially been meaningless, and he dismissed the notion that Obama was in any position to empower Cubans.

"The Cuban people empowered themselves decades ago," Rodriguez said, referring to the 1959 revolution that put the current government in power. He said if Obama was preoccupied with empowering Cubans, "something must be going wrong in U.S. democracy."

Obama's aides and supporters in Congress brushed off such tough talk from Cuban officials. They argue that decades of a U.S. policy of isolation that failed to bring about change in Cuba illustrated why engaging with the island is worthwhile.

Yet Obama's opponents insist he is rewarding a government that has yet to show it is serious about improving human rights and opening up its economy and political system. Though Obama has been rolling back restrictions on Cuba through regulatory moves, he has been unable to persuade Congress to lift the U.S. trade embargo, a chief Cuban demand.

Two years after taking power in 2008, Raul Castro launched economic and social reforms that appear slow-moving to many Cubans and foreigners, but are lasting and widespread within Cuban society.

The changes have allowed hundreds of thousands of people to work in the private sector and have relaxed limits on cellphones, Internet and Cubans' comfort with discussing their country's problems in public, for example.

The Cuban government has been unyielding, however, on making changes to its single-party political system and to the strict limits on media, public speech, assembly and dissent.

While in Havana, Obama will attend a state dinner in his honor and lay a wreath at a memorial to Jose Marti, a Cuban independence hero. He will give a speech at the Grand Theater of Havana -- carried on Cuban television. White House aides said Obama will lay out a vision of greater freedoms and economic opportunity.

Ahead of his trip, Obama announced moves to further lift U.S. restrictions on Cuba, including easing travel restrictions for Americans and restoring Cuba's access to the global financial system. Cuba has been slower to approve U.S. businesses operating in Cuba and to take other steps sought by the U.S. But Cuba did announce plans to lift a 10 percent conversion fee on U.S. dollars.

The jubilation that surged through Cuba in the early days of detente has been tempered by the absence of tangible improvement in most people's lives. Obama is well-regarded in Cuba, and though his trip has spurred excitement in the country, few Cubans expect to see Obama in person. The Castro government has announced a virtual shutdown of Havana during Obama's stay.

"I don't think things are going to improve here," said Rosa Lopez, a 52-year-old food stand worker. Gesturing at her worn-out sandals and soft drinks for sale, she added, "All this is here, in this country, and the United States is way over there."

Obama's trip comes in the midst of a heated U.S. presidential election in which his willingness to talk to America's foes -- not only Cuba, but also Iran -- has been a focus.

Democratic presidential front-runner Hillary Clinton has embraced much of his foreign policy agenda, including the Cuba opening. But Republican candidates describe Obama's outreach to Castro as part of a pattern of naïve overtures to enemies that has yielded little in return.

Against that backdrop, Obama aims to avoid glaring missteps that could make a rollback of his Cuba policy more palatable to Americans. He hopes a successful trip will make that impossible, even if a Republican is elected in November.

"We very much want to make the process of normalization irreversible," said Ben Rhodes, Obama's deputy national security adviser.